Various types of telecopier machines are known which are capable of sending and receiving fax messages through a telephone line. The machines ordinarily incorporate printers or, e.g., of the Dotmatrix type. The said printers have buffer memory means for storing digital information corresponding to one line of print and thereafter printing the said line while the information corresponding to another line is received and stored. In this specification the word "print" will be used to indicate any signs that are to be transmitted and received as part of fax messages, be they characters representing letters and words or drawings or graphic signs of any other kind. Telecopier machines are therefore capable of sending and/or receiving a message, and no message can be received while the machine is engaged in sending another one.